stable_bst 0.2.0

// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

use std::cmp::Ordering::{self, Less, Equal, Greater};
use std::default::Default;
use std::fmt::{self, Debug};
use std::iter::{self, Peekable, IntoIterator};
use std::hash::{Hash, Hasher};
use std::ops;

use compare::{Compare, Natural, natural};
use super::map::{self, Forward, TreeMap};
use super::Bound;

// FIXME(conventions): implement bounded iterators
// FIXME(conventions): replace rev_iter(_mut) by making iter(_mut) DoubleEnded

/// An implementation of a set on top of the `TreeMap` container.
///
/// # Examples
///
/// ```{rust}
/// use stable_bst::TreeSet;
///
/// let mut set = TreeSet::new();
///
/// set.insert(2);
/// set.insert(1);
/// set.insert(3);
///
/// for i in set.iter() {
///    println!("{}", i) // prints 1, then 2, then 3
/// }
///
/// set.remove(&3);
///
/// if !set.contains(&3) {
///     println!("set does not contain a 3 anymore");
/// }
/// ```
///
/// A `TreeSet` can also be used with a custom ordering:
///
/// ```rust
/// use stable_bst::TreeSet;
///
/// struct Troll<'a> {
///     name: &'a str,
///     level: u32,
/// }
///
/// let mut trolls = TreeSet::with_comparator(|l: &Troll, r: &Troll| l.level.cmp(&r.level));
///
/// trolls.insert(Troll { name: "Orgarr", level: 2 });
/// trolls.insert(Troll { name: "Blargarr", level: 3 });
/// trolls.insert(Troll { name: "Kron the Smelly One", level: 4 });
/// trolls.insert(Troll { name: "Wartilda", level: 1 });
///
/// println!("You are facing {} trolls!", trolls.len());
///
/// // Print the trolls, ordered by level with smallest level first
/// for x in trolls.iter() {
///     println!("level {}: {}!", x.level, x.name);
/// }
///
/// // Kill all trolls
/// trolls.clear();
/// assert_eq!(trolls.len(), 0);
/// ```
#[derive(Clone)]
pub struct TreeSet<T, C: Compare<T> = Natural<T>> {
    map: TreeMap<T, (), C>,
}

// FIXME: determine what `PartialEq` means for comparator-based `TreeSet`s
impl<T: PartialEq + Ord> PartialEq for TreeSet<T> {
    #[inline]
    fn eq(&self, other: &TreeSet<T>) -> bool {
        self.map == other.map
    }
}

// FIXME: determine what `Eq` means for comparator-based `TreeSet`s
impl<T: Eq + Ord> Eq for TreeSet<T> {}

// FIXME: determine what `PartialOrd` means for comparator-based `TreeSet`s
impl<T: Ord> PartialOrd for TreeSet<T> {
    #[inline]
    fn partial_cmp(&self, other: &TreeSet<T>) -> Option<Ordering> {
        self.map.partial_cmp(&other.map)
    }
}

// FIXME: determine what `Ord` means for comparator-based `TreeSet`s
impl<T: Ord> Ord for TreeSet<T> {
    #[inline]
    fn cmp(&self, other: &TreeSet<T>) -> Ordering {
        self.iter().cmp(other)
    }
}

impl<T: Debug, C> Debug for TreeSet<T, C>
    where C: Compare<T>
{
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        try!(write!(f, "{{"));

        for (i, x) in self.iter().enumerate() {
            if i != 0 {
                try!(write!(f, ", "));
            }
            try!(write!(f, "{:?}", *x));
        }

        write!(f, "}}")
    }
}

impl<T, C> Default for TreeSet<T, C>
    where C: Compare<T> + Default
{
    #[inline]
    fn default() -> TreeSet<T, C> {
        TreeSet::with_comparator(Default::default())
    }
}

impl<T: Ord> TreeSet<T> {
    /// Creates an empty `TreeSet` ordered according to the natural order of its values.
    ///
    /// # Examples
    ///
    /// ```rust
    /// use stable_bst::TreeSet;
    /// let mut set: TreeSet<i32> = TreeSet::new();
    /// ```
    #[inline]
    pub fn new() -> TreeSet<T> {
        TreeSet::with_comparator(natural())
    }
}

impl<T, C> TreeSet<T, C>
    where C: Compare<T>
{
    /// Creates an empty `TreeSet` ordered according to the given comparator.
    pub fn with_comparator(cmp: C) -> TreeSet<T, C> {
        TreeSet { map: TreeMap::with_comparator(cmp) }
    }

    /// Returns the comparator according to which the `TreeSet` is ordered.
    pub fn comparator(&self) -> &C {
        self.map.comparator()
    }

    /// Gets a lazy iterator over the values in the set, in ascending order.
    ///
    /// # Examples
    ///
    /// ```rust
    /// use stable_bst::TreeSet;
    /// let set: TreeSet<i32> = [1, 4, 3, 5, 2].iter().map(|&x| x).collect();
    ///
    /// // Will print in ascending order.
    /// for x in set.iter() {
    ///     println!("{}", x);
    /// }
    /// ```
    #[inline]
    pub fn iter(&self) -> Iter<T> {
        Iter { iter: self.map.iter() }
    }

    /// Creates a consuming iterator, that is, one that moves each value out of the
    /// set in ascending order. The set cannot be used after calling this.
    ///
    /// # Examples
    ///
    /// ```rust
    /// use stable_bst::TreeSet;
    /// let set: TreeSet<i32> = [1, 4, 3, 5, 2].iter().map(|&x| x).collect();
    ///
    /// // Not possible with a regular `.iter()`
    /// let v: Vec<i32> = set.into_iter().collect();
    /// assert_eq!(v, vec![1, 2, 3, 4, 5]);
    /// ```
    #[inline]
    pub fn into_iter(self) -> IntoIter<T> {
        fn first<A, B>((a, _): (A, B)) -> A {
            a
        }
        let first: fn((T, ())) -> T = first; // coerce to fn pointer

        IntoIter(self.map.into_iter().map(first))
    }

    /// Constructs a double-ended iterator over a sub-range of elements in the set, starting
    /// at min, and ending at max. If min is `Unbounded`, then it will be treated as "negative
    /// infinity", and if max is `Unbounded`, then it will be treated as "positive infinity".
    /// Thus range(Unbounded, Unbounded) will yield the whole collection.
    ///
    /// # Examples
    ///
    /// ```
    /// use stable_bst::TreeSet;
    /// use stable_bst::Bound::{Included, Unbounded};
    ///
    /// let mut set = TreeSet::new();
    /// set.insert(3);
    /// set.insert(5);
    /// set.insert(8);
    /// for &elem in set.range(Included(&4), Included(&8)) {
    ///     println!("{}", elem);
    /// }
    /// assert_eq!(Some(&5), set.range(Included(&4), Unbounded).next());
    /// ```
    pub fn range<'a, Min: ?Sized, Max: ?Sized>(&'a self,
                                               min: Bound<&Min>,
                                               max: Bound<&Max>)
                                               -> Range<'a, T>
        where C: Compare<Min, T> + Compare<Max, T>
    {
        Range { range: self.map.range(min, max) }
    }

    /// Visits the values representing the difference, in ascending order.
    ///
    /// # Examples
    ///
    /// ```rust
    /// use stable_bst::TreeSet;
    ///
    /// let a: TreeSet<i32> = [1, 2, 3].iter().map(|&x| x).collect();
    /// let b: TreeSet<i32> = [3, 4, 5].iter().map(|&x| x).collect();
    ///
    /// // Can be seen as `a - b`.
    /// for x in a.difference(&b) {
    ///     println!("{}", x); // Print 1 then 2
    /// }
    ///
    /// let diff: TreeSet<i32> = a.difference(&b).map(|&x| x).collect();
    /// assert_eq!(diff, [1, 2].iter().map(|&x| x).collect());
    ///
    /// // Note that difference is not symmetric,
    /// // and `b - a` means something else:
    /// let diff: TreeSet<i32> = b.difference(&a).map(|&x| x).collect();
    /// assert_eq!(diff, [4, 5].iter().map(|&x| x).collect());
    /// ```
    pub fn difference<'a>(&'a self, other: &'a TreeSet<T, C>) -> Difference<'a, T, C>
        where C: Eq
    {
        assert!(self.comparator() == other.comparator());
        Difference {
            a: self.iter().peekable(),
            b: other.iter().peekable(),
            cmp: self.comparator(),
        }
    }

    /// Visits the values representing the symmetric difference, in ascending order.
    ///
    /// # Examples
    ///
    /// ```rust
    /// use stable_bst::TreeSet;
    ///
    /// let a: TreeSet<i32> = [1, 2, 3].iter().map(|&x| x).collect();
    /// let b: TreeSet<i32> = [3, 4, 5].iter().map(|&x| x).collect();
    ///
    /// // Print 1, 2, 4, 5 in ascending order.
    /// for x in a.symmetric_difference(&b) {
    ///     println!("{}", x);
    /// }
    ///
    /// let diff1: TreeSet<i32> = a.symmetric_difference(&b).map(|&x| x).collect();
    /// let diff2: TreeSet<i32> = b.symmetric_difference(&a).map(|&x| x).collect();
    ///
    /// assert_eq!(diff1, diff2);
    /// assert_eq!(diff1, [1, 2, 4, 5].iter().map(|&x| x).collect());
    /// ```
    pub fn symmetric_difference<'a>(&'a self,
                                    other: &'a TreeSet<T, C>)
                                    -> SymmetricDifference<'a, T, C>
        where C: Eq
    {
        assert!(self.comparator() == other.comparator());
        SymmetricDifference {
            a: self.iter().peekable(),
            b: other.iter().peekable(),
            cmp: self.comparator(),
        }
    }

    /// Visits the values representing the intersection, in ascending order.
    ///
    /// # Examples
    ///
    /// ```rust
    /// use stable_bst::TreeSet;
    ///
    /// let a: TreeSet<i32> = [1, 2, 3].iter().map(|&x| x).collect();
    /// let b: TreeSet<i32> = [2, 3, 4].iter().map(|&x| x).collect();
    ///
    /// // Print 2, 3 in ascending order.
    /// for x in a.intersection(&b) {
    ///     println!("{}", x);
    /// }
    ///
    /// let diff: TreeSet<i32> = a.intersection(&b).map(|&x| x).collect();
    /// assert_eq!(diff, [2, 3].iter().map(|&x| x).collect());
    /// ```
    pub fn intersection<'a>(&'a self, other: &'a TreeSet<T, C>) -> Intersection<'a, T, C>
        where C: Eq
    {
        assert!(self.comparator() == other.comparator());
        Intersection {
            a: self.iter().peekable(),
            b: other.iter().peekable(),
            cmp: self.comparator(),
        }
    }

    /// Visits the values representing the union, in ascending order.
    ///
    /// # Examples
    ///
    /// ```rust
    /// use stable_bst::TreeSet;
    ///
    /// let a: TreeSet<i32> = [1, 2, 3].iter().map(|&x| x).collect();
    /// let b: TreeSet<i32> = [3, 4, 5].iter().map(|&x| x).collect();
    ///
    /// // Print 1, 2, 3, 4, 5 in ascending order.
    /// for x in a.union(&b) {
    ///     println!("{}", x);
    /// }
    ///
    /// let diff: TreeSet<i32> = a.union(&b).map(|&x| x).collect();
    /// assert_eq!(diff, [1, 2, 3, 4, 5].iter().map(|&x| x).collect());
    /// ```
    pub fn union<'a>(&'a self, other: &'a TreeSet<T, C>) -> Union<'a, T, C>
        where C: Eq
    {
        assert!(self.comparator() == other.comparator());
        Union {
            a: self.iter().peekable(),
            b: other.iter().peekable(),
            cmp: self.comparator(),
        }
    }

    /// Return the number of elements in the set
    ///
    /// # Examples
    ///
    /// ```rust
    /// use stable_bst::TreeSet;
    ///
    /// let mut v = TreeSet::new();
    /// assert_eq!(v.len(), 0);
    /// v.insert(1);
    /// assert_eq!(v.len(), 1);
    /// ```
    #[inline]
    pub fn len(&self) -> usize {
        self.map.len()
    }

    /// Returns true if the set contains no elements
    ///
    /// # Examples
    ///
    /// ```rust
    /// use stable_bst::TreeSet;
    ///
    /// let mut v = TreeSet::new();
    /// assert!(v.is_empty());
    /// v.insert(1);
    /// assert!(!v.is_empty());
    /// ```
    pub fn is_empty(&self) -> bool {
        self.len() == 0
    }

    /// Clears the set, removing all values.
    ///
    /// # Examples
    ///
    /// ```rust
    /// use stable_bst::TreeSet;
    ///
    /// let mut v = TreeSet::new();
    /// v.insert(1);
    /// v.clear();
    /// assert!(v.is_empty());
    /// ```
    #[inline]
    pub fn clear(&mut self) {
        self.map.clear()
    }

    /// Returns `true` if the set contains a value.
    ///
    /// The value may be any borrowed form of the set's value type,
    /// but the ordering on the borrowed form *must* match the
    /// ordering on the value type.
    ///
    /// # Examples
    ///
    /// ```rust
    /// use stable_bst::TreeSet;
    ///
    /// let set: TreeSet<i32> = [1, 2, 3].iter().map(|&x| x).collect();
    /// assert_eq!(set.contains(&1), true);
    /// assert_eq!(set.contains(&4), false);
    /// ```
    #[inline]
    pub fn contains<Q: ?Sized>(&self, value: &Q) -> bool
        where C: Compare<Q, T>
    {
        self.map.contains_key(value)
    }

    /// Returns `true` if the set has no elements in common with `other`.
    /// This is equivalent to checking for an empty intersection.
    ///
    /// # Examples
    ///
    /// ```rust
    /// use stable_bst::TreeSet;
    ///
    /// let a: TreeSet<i32> = [1, 2, 3].iter().map(|&x| x).collect();
    /// let mut b: TreeSet<i32> = TreeSet::new();
    ///
    /// assert_eq!(a.is_disjoint(&b), true);
    /// b.insert(4);
    /// assert_eq!(a.is_disjoint(&b), true);
    /// b.insert(1);
    /// assert_eq!(a.is_disjoint(&b), false);
    /// ```
    pub fn is_disjoint(&self, other: &TreeSet<T, C>) -> bool
        where C: Eq
    {
        self.intersection(other).next().is_none()
    }

    /// Returns `true` if the set is a subset of another.
    ///
    /// # Examples
    ///
    /// ```rust
    /// use stable_bst::TreeSet;
    ///
    /// let sup: TreeSet<i32> = [1, 2, 3].iter().map(|&x| x).collect();
    /// let mut set: TreeSet<i32> = TreeSet::new();
    ///
    /// assert_eq!(set.is_subset(&sup), true);
    /// set.insert(2);
    /// assert_eq!(set.is_subset(&sup), true);
    /// set.insert(4);
    /// assert_eq!(set.is_subset(&sup), false);
    /// ```
    pub fn is_subset(&self, other: &TreeSet<T, C>) -> bool
        where C: Eq
    {
        assert!(self.comparator() == other.comparator());
        let mut x = self.iter();
        let mut y = other.iter();
        let mut a = x.next();
        let mut b = y.next();
        while a.is_some() {
            if b.is_none() {
                return false;
            }

            let a1 = a.unwrap();
            let b1 = b.unwrap();

            match self.comparator().compare(b1, a1) {
                Less => (),
                Greater => return false,
                Equal => a = x.next(),
            }

            b = y.next();
        }
        true
    }

    /// Returns `true` if the set is a superset of another.
    ///
    /// # Examples
    ///
    /// ```rust
    /// use stable_bst::TreeSet;
    ///
    /// let sub: TreeSet<i32> = [1, 2].iter().map(|&x| x).collect();
    /// let mut set: TreeSet<i32> = TreeSet::new();
    ///
    /// assert_eq!(set.is_superset(&sub), false);
    ///
    /// set.insert(0);
    /// set.insert(1);
    /// assert_eq!(set.is_superset(&sub), false);
    ///
    /// set.insert(2);
    /// assert_eq!(set.is_superset(&sub), true);
    /// ```
    pub fn is_superset(&self, other: &TreeSet<T, C>) -> bool
        where C: Eq
    {
        other.is_subset(self)
    }

    /// Adds a value to the set. Returns `true` if the value was not already
    /// present in the set.
    ///
    /// # Examples
    ///
    /// ```rust
    /// use stable_bst::TreeSet;
    ///
    /// let mut set = TreeSet::new();
    ///
    /// assert_eq!(set.insert(2), true);
    /// assert_eq!(set.insert(2), false);
    /// assert_eq!(set.len(), 1);
    /// ```
    #[inline]
    pub fn insert(&mut self, value: T) -> bool {
        self.map.insert(value, ()).is_none()
    }

    /// Removes a value from the set. Returns `true` if the value was
    /// present in the set.
    ///
    /// The value may be any borrowed form of the set's value type,
    /// but the ordering on the borrowed form *must* match the
    /// ordering on the value type.
    ///
    /// # Examples
    ///
    /// ```rust
    /// use stable_bst::TreeSet;
    ///
    /// let mut set = TreeSet::new();
    ///
    /// set.insert(2);
    /// assert_eq!(set.remove(&2), true);
    /// assert_eq!(set.remove(&2), false);
    /// ```
    #[inline]
    pub fn remove<Q: ?Sized>(&mut self, value: &Q) -> bool
        where C: Compare<Q, T>
    {
        self.map.remove(value).is_some()
    }
}

/// A lazy forward iterator over a set.
pub struct Iter<'a, T: 'a> {
    iter: map::Iter<'a, T, (), Forward>,
}

pub struct Range<'a, T: 'a> {
    range: map::Range<'a, T, ()>,
}

/// A lazy forward iterator over a set that consumes the set while iterating.
pub struct IntoIter<T>(iter::Map<map::IntoIter<T, ()>, fn((T, ())) -> T>);

/// A lazy iterator producing elements in the set difference (in-order).
pub struct Difference<'a, T: 'a, C: 'a> {
    a: Peekable<Iter<'a, T>>,
    b: Peekable<Iter<'a, T>>,
    cmp: &'a C,
}

/// A lazy iterator producing elements in the set symmetric difference (in-order).
pub struct SymmetricDifference<'a, T: 'a, C: 'a> {
    a: Peekable<Iter<'a, T>>,
    b: Peekable<Iter<'a, T>>,
    cmp: &'a C,
}

/// A lazy iterator producing elements in the set intersection (in-order).
pub struct Intersection<'a, T: 'a, C: 'a> {
    a: Peekable<Iter<'a, T>>,
    b: Peekable<Iter<'a, T>>,
    cmp: &'a C,
}

/// A lazy iterator producing elements in the set union (in-order).
pub struct Union<'a, T: 'a, C: 'a> {
    a: Peekable<Iter<'a, T>>,
    b: Peekable<Iter<'a, T>>,
    cmp: &'a C,
}

/// Compare `x` and `y`, but return `short` if x is None and `long` if y is None
fn cmp_opt<T, C: Compare<T>>(x: Option<&&T>,
                             y: Option<&&T>,
                             short: Ordering,
                             long: Ordering,
                             cmp: &C)
                             -> Ordering {
    match (x, y) {
        (None, _) => short,
        (_, None) => long,
        (Some(x1), Some(y1)) => cmp.compare(*x1, *y1),
    }
}

impl<'a, T> Iterator for Iter<'a, T> {
    type Item = &'a T;
    #[inline]
    fn next(&mut self) -> Option<&'a T> {
        self.iter.next().map(|(value, _)| value)
    }
    #[inline]
    fn size_hint(&self) -> (usize, Option<usize>) {
        self.iter.size_hint()
    }
}

impl<'a, T> Iterator for Range<'a, T> {
    type Item = &'a T;
    #[inline]
    fn next(&mut self) -> Option<&'a T> {
        self.range.next().map(|(value, _)| value)
    }
}

impl<'a, T> DoubleEndedIterator for Range<'a, T> {
    #[inline]
    fn next_back(&mut self) -> Option<&'a T> {
        self.range.next_back().map(|(value, _)| value)
    }
}

impl<T> Iterator for IntoIter<T> {
    type Item = T;
    #[inline]
    fn next(&mut self) -> Option<T> {
        self.0.next()
    }
    #[inline]
    fn size_hint(&self) -> (usize, Option<usize>) {
        self.0.size_hint()
    }
}

impl<'a, T, C> Iterator for Difference<'a, T, C>
    where C: Compare<T>
{
    type Item = &'a T;
    fn next(&mut self) -> Option<&'a T> {
        loop {
            match cmp_opt(self.a.peek(), self.b.peek(), Less, Less, self.cmp) {
                Less => return self.a.next(),
                Equal => {
                    self.a.next();
                    self.b.next();
                }
                Greater => {
                    self.b.next();
                }
            }
        }
    }
}

impl<'a, T, C> Iterator for SymmetricDifference<'a, T, C>
    where C: Compare<T>
{
    type Item = &'a T;
    fn next(&mut self) -> Option<&'a T> {
        loop {
            match cmp_opt(self.a.peek(), self.b.peek(), Greater, Less, self.cmp) {
                Less => return self.a.next(),
                Equal => {
                    self.a.next();
                    self.b.next();
                }
                Greater => return self.b.next(),
            }
        }
    }
}

impl<'a, T, C> Iterator for Intersection<'a, T, C>
    where C: Compare<T>
{
    type Item = &'a T;
    fn next(&mut self) -> Option<&'a T> {
        loop {
            let o_cmp = match (self.a.peek(), self.b.peek()) {
                (None, _) => None,
                (_, None) => None,
                (Some(a1), Some(b1)) => Some(self.cmp.compare(*a1, *b1)),
            };
            match o_cmp {
                None => return None,
                Some(Less) => {
                    self.a.next();
                }
                Some(Equal) => {
                    self.b.next();
                    return self.a.next();
                }
                Some(Greater) => {
                    self.b.next();
                }
            }
        }
    }
}

impl<'a, T, C> Iterator for Union<'a, T, C>
    where C: Compare<T>
{
    type Item = &'a T;
    fn next(&mut self) -> Option<&'a T> {
        loop {
            match cmp_opt(self.a.peek(), self.b.peek(), Greater, Less, self.cmp) {
                Less => return self.a.next(),
                Equal => {
                    self.b.next();
                    return self.a.next();
                }
                Greater => return self.b.next(),
            }
        }
    }
}

impl<'a, 'b, T, C> ops::BitOr<&'b TreeSet<T, C>> for &'a TreeSet<T, C>
    where T: Clone,
          C: Compare<T> + Eq + Clone
{
    type Output = TreeSet<T, C>;

    /// Returns the union of `self` and `rhs` as a new `TreeSet<T, C>`.
    ///
    /// # Examples
    ///
    /// ```rust
    /// use stable_bst::TreeSet;
    ///
    /// let a: TreeSet<i32> = vec![1, 2, 3].into_iter().collect();
    /// let b: TreeSet<i32> = vec![3, 4, 5].into_iter().collect();
    ///
    /// let set: TreeSet<i32> = &a | &b;
    /// let v: Vec<i32> = set.into_iter().collect();
    /// assert_eq!(v, vec![1, 2, 3, 4, 5]);
    /// ```
    fn bitor(self, rhs: &TreeSet<T, C>) -> TreeSet<T, C> {
        let it = self.union(rhs).cloned();
        let mut set = TreeSet::with_comparator(self.comparator().clone());
        set.extend(it);
        set
    }
}

impl<'a, 'b, T, C> ops::BitAnd<&'b TreeSet<T, C>> for &'a TreeSet<T, C>
    where T: Clone,
          C: Compare<T> + Eq + Clone
{
    type Output = TreeSet<T, C>;

    /// Returns the intersection of `self` and `rhs` as a new `TreeSet<T, C>`.
    ///
    /// # Examples
    ///
    /// ```rust
    /// use stable_bst::TreeSet;
    ///
    /// let a: TreeSet<i32> = vec![1, 2, 3].into_iter().collect();
    /// let b: TreeSet<i32> = vec![2, 3, 4].into_iter().collect();
    ///
    /// let set: TreeSet<i32> = &a & &b;
    /// let v: Vec<i32> = set.into_iter().collect();
    /// assert_eq!(v, vec![2, 3]);
    /// ```
    fn bitand(self, rhs: &TreeSet<T, C>) -> TreeSet<T, C> {
        let it = self.intersection(rhs).cloned();
        let mut set = TreeSet::with_comparator(self.comparator().clone());
        set.extend(it);
        set
    }
}

impl<'a, 'b, T, C> ops::BitXor<&'b TreeSet<T, C>> for &'a TreeSet<T, C>
    where T: Clone,
          C: Compare<T> + Eq + Clone
{
    type Output = TreeSet<T, C>;

    /// Returns the symmetric difference of `self` and `rhs` as a new `TreeSet<T, C>`.
    ///
    /// # Examples
    ///
    /// ```rust
    /// use stable_bst::TreeSet;
    ///
    /// let a: TreeSet<i32> = vec![1, 2, 3].into_iter().collect();
    /// let b: TreeSet<i32> = vec![3, 4, 5].into_iter().collect();
    ///
    /// let set: TreeSet<i32> = &a ^ &b;
    /// let v: Vec<i32> = set.into_iter().collect();
    /// assert_eq!(v, vec![1, 2, 4, 5]);
    /// ```
    fn bitxor(self, rhs: &TreeSet<T, C>) -> TreeSet<T, C> {
        let it = self.symmetric_difference(rhs).cloned();
        let mut set = TreeSet::with_comparator(self.comparator().clone());
        set.extend(it);
        set
    }
}

impl<'a, 'b, T, C> ops::Sub<&'b TreeSet<T, C>> for &'a TreeSet<T, C>
    where T: Clone,
          C: Compare<T> + Eq + Clone
{
    type Output = TreeSet<T, C>;

    /// Returns the difference of `self` and `rhs` as a new `TreeSet<T, C>`.
    ///
    /// # Examples
    ///
    /// ```rust
    /// use stable_bst::TreeSet;
    ///
    /// let a: TreeSet<i32> = vec![1, 2, 3].into_iter().collect();
    /// let b: TreeSet<i32> = vec![3, 4, 5].into_iter().collect();
    ///
    /// let set: TreeSet<i32> = &a - &b;
    /// let v: Vec<i32> = set.into_iter().collect();
    /// assert_eq!(v, vec![1, 2]);
    /// ```
    fn sub(self, rhs: &TreeSet<T, C>) -> TreeSet<T, C> {
        let it = self.difference(rhs).cloned();
        let mut set = TreeSet::with_comparator(self.comparator().clone());
        set.extend(it);
        set
    }
}

impl<T, C> iter::FromIterator<T> for TreeSet<T, C>
    where C: Compare<T> + Default
{
    fn from_iter<Iter: IntoIterator<Item = T>>(iter: Iter) -> TreeSet<T, C> {
        let mut set: TreeSet<T, C> = Default::default();
        set.extend(iter);
        set
    }
}

impl<T, C> Extend<T> for TreeSet<T, C>
    where C: Compare<T>
{
    #[inline]
    fn extend<Iter: IntoIterator<Item = T>>(&mut self, iter: Iter) {
        for elem in iter {
            self.insert(elem);
        }
    }
}


impl<T: Hash, C> Hash for TreeSet<T, C>
    where C: Compare<T>
{
    fn hash<H: Hasher>(&self, state: &mut H) {
        for elt in self.iter() {
            elt.hash(state);
        }
    }
}

impl<'a, T, C> IntoIterator for &'a TreeSet<T, C>
    where C: Compare<T>
{
    type Item = &'a T;
    type IntoIter = Iter<'a, T>;
    fn into_iter(self) -> Iter<'a, T> {
        self.iter()
    }
}

impl<T, C> IntoIterator for TreeSet<T, C>
    where C: Compare<T>
{
    type Item = T;
    type IntoIter = IntoIter<T>;
    fn into_iter(self) -> IntoIter<T> {
        self.into_iter()
    }
}

#[cfg(feature="ordered_iter")]
impl<'a, K> ::ordered_iter::OrderedSetIterator for Iter<'a, K> {}

#[cfg(test)]
mod test {
    use std::hash;
    use std::hash::Hasher;

    use super::TreeSet;

    fn hash<T: hash::Hash>(t: &T) -> u64 {
        let mut s = hash::SipHasher::new();
        t.hash(&mut s);
        s.finish()
    }

    #[test]
    fn test_clear() {
        let mut s = TreeSet::new();
        s.clear();
        assert!(s.insert(5));
        assert!(s.insert(12));
        assert!(s.insert(19));
        s.clear();
        assert!(!s.contains(&5));
        assert!(!s.contains(&12));
        assert!(!s.contains(&19));
        assert!(s.is_empty());
    }

    #[test]
    fn test_disjoint() {
        let mut xs = TreeSet::new();
        let mut ys = TreeSet::new();
        assert!(xs.is_disjoint(&ys));
        assert!(ys.is_disjoint(&xs));
        assert!(xs.insert(5));
        assert!(ys.insert(11));
        assert!(xs.is_disjoint(&ys));
        assert!(ys.is_disjoint(&xs));
        assert!(xs.insert(7));
        assert!(xs.insert(19));
        assert!(xs.insert(4));
        assert!(ys.insert(2));
        assert!(ys.insert(-11));
        assert!(xs.is_disjoint(&ys));
        assert!(ys.is_disjoint(&xs));
        assert!(ys.insert(7));
        assert!(!xs.is_disjoint(&ys));
        assert!(!ys.is_disjoint(&xs));
    }

    #[test]
    fn test_subset_and_superset() {
        let mut a = TreeSet::new();
        assert!(a.insert(0));
        assert!(a.insert(5));
        assert!(a.insert(11));
        assert!(a.insert(7));

        let mut b = TreeSet::new();
        assert!(b.insert(0));
        assert!(b.insert(7));
        assert!(b.insert(19));
        assert!(b.insert(250));
        assert!(b.insert(11));
        assert!(b.insert(200));

        assert!(!a.is_subset(&b));
        assert!(!a.is_superset(&b));
        assert!(!b.is_subset(&a));
        assert!(!b.is_superset(&a));

        assert!(b.insert(5));

        assert!(a.is_subset(&b));
        assert!(!a.is_superset(&b));
        assert!(!b.is_subset(&a));
        assert!(b.is_superset(&a));
    }

    #[test]
    fn test_iterator() {
        let mut m = TreeSet::new();

        assert!(m.insert(3));
        assert!(m.insert(0));
        assert!(m.insert(4));
        assert!(m.insert(2));
        assert!(m.insert(1));

        let mut n = 0;
        for x in m.iter() {
            assert_eq!(*x, n);
            n += 1
        }
    }

    #[test]
    fn test_move_iter() {
        let s: TreeSet<i32> = (0..5).collect();

        let mut n = 0;
        for x in s.into_iter() {
            assert_eq!(x, n);
            n += 1;
        }
    }

    #[test]
    fn test_move_iter_size_hint() {
        let s: TreeSet<i32> = vec![0, 1].into_iter().collect();

        let mut it = s.into_iter();

        assert_eq!(it.size_hint(), (2, Some(2)));
        assert!(it.next() != None);

        assert_eq!(it.size_hint(), (1, Some(1)));
        assert!(it.next() != None);

        assert_eq!(it.size_hint(), (0, Some(0)));
        assert_eq!(it.next(), None);
    }

    #[test]
    fn test_clone_eq() {
        let mut m = TreeSet::new();

        m.insert(1);
        m.insert(2);

        assert!(m.clone() == m);
    }

    #[test]
    fn test_hash() {
        let mut x = TreeSet::new();
        let mut y = TreeSet::new();

        x.insert(1);
        x.insert(2);
        x.insert(3);

        y.insert(3);
        y.insert(2);
        y.insert(1);

        assert!(hash(&x) == hash(&y));
    }

    fn check<F>(a: &[i32], b: &[i32], expected: &[i32], f: F)
        where F: FnOnce(&TreeSet<i32>, &TreeSet<i32>) -> Vec<i32>
    {
        let mut set_a = TreeSet::new();
        let mut set_b = TreeSet::new();

        for x in a.iter() {
            assert!(set_a.insert(*x))
        }
        for y in b.iter() {
            assert!(set_b.insert(*y))
        }

        let list = f(&set_a, &set_b);
        assert_eq!(list, expected);
    }

    #[test]
    fn test_intersection() {
        fn check_intersection(a: &[i32], b: &[i32], expected: &[i32]) {
            check(a,
                  b,
                  expected,
                  |x, y| x.intersection(y).map(|v| *v).collect::<Vec<i32>>())
        }

        check_intersection(&[], &[], &[]);
        check_intersection(&[1, 2, 3], &[], &[]);
        check_intersection(&[], &[1, 2, 3], &[]);
        check_intersection(&[2], &[1, 2, 3], &[2]);
        check_intersection(&[1, 2, 3], &[2], &[2]);
        check_intersection(&[11, 1, 3, 77, 103, 5, -5],
                           &[2, 11, 77, -9, -42, 5, 3],
                           &[3, 5, 11, 77]);
    }

    #[test]
    fn test_difference() {
        fn check_difference(a: &[i32], b: &[i32], expected: &[i32]) {
            check(a,
                  b,
                  expected,
                  |x, y| x.difference(y).map(|v| *v).collect::<Vec<i32>>())
        }

        check_difference(&[], &[], &[]);
        check_difference(&[1, 12], &[], &[1, 12]);
        check_difference(&[], &[1, 2, 3, 9], &[]);
        check_difference(&[1, 3, 5, 9, 11], &[3, 9], &[1, 5, 11]);
        check_difference(&[-5, 11, 22, 33, 40, 42],
                         &[-12, -5, 14, 23, 34, 38, 39, 50],
                         &[11, 22, 33, 40, 42]);
    }

    #[test]
    fn test_symmetric_difference() {
        fn check_symmetric_difference(a: &[i32], b: &[i32], expected: &[i32]) {
            check(a,
                  b,
                  expected,
                  |x, y| x.symmetric_difference(y).map(|v| *v).collect::<Vec<i32>>())
        }

        check_symmetric_difference(&[], &[], &[]);
        check_symmetric_difference(&[1, 2, 3], &[2], &[1, 3]);
        check_symmetric_difference(&[2], &[1, 2, 3], &[1, 3]);
        check_symmetric_difference(&[1, 3, 5, 9, 11],
                                   &[-2, 3, 9, 14, 22],
                                   &[-2, 1, 5, 11, 14, 22]);
    }

    #[test]
    fn test_union() {
        fn check_union(a: &[i32], b: &[i32], expected: &[i32]) {
            check(a,
                  b,
                  expected,
                  |x, y| x.union(y).map(|v| *v).collect::<Vec<i32>>())
        }

        check_union(&[], &[], &[]);
        check_union(&[1, 2, 3], &[2], &[1, 2, 3]);
        check_union(&[2], &[1, 2, 3], &[1, 2, 3]);
        check_union(&[1, 3, 5, 9, 11, 16, 19, 24],
                    &[-2, 1, 5, 9, 13, 19],
                    &[-2, 1, 3, 5, 9, 11, 13, 16, 19, 24]);
    }

    #[test]
    fn test_bit_or() {
        let a: TreeSet<i32> = vec![1, 3, 5, 9, 11, 16, 19, 24].into_iter().collect();
        let b: TreeSet<i32> = vec![-2, 1, 5, 9, 13, 19].into_iter().collect();

        let set: TreeSet<i32> = &a | &b;
        let v: Vec<i32> = set.into_iter().collect();
        assert_eq!(v, vec![-2, 1, 3, 5, 9, 11, 13, 16, 19, 24]);
    }

    #[test]
    fn test_bit_and() {
        let a: TreeSet<i32> = vec![11, 1, 3, 77, 103, 5, -5].into_iter().collect();
        let b: TreeSet<i32> = vec![2, 11, 77, -9, -42, 5, 3].into_iter().collect();

        let set: TreeSet<i32> = &a & &b;
        let v: Vec<i32> = set.into_iter().collect();
        assert_eq!(v, vec![3, 5, 11, 77]);
    }

    #[test]
    fn test_bit_xor() {
        let a: TreeSet<i32> = vec![1, 3, 5, 9, 11].into_iter().collect();
        let b: TreeSet<i32> = vec![-2, 3, 9, 14, 22].into_iter().collect();

        let set: TreeSet<i32> = &a ^ &b;
        let v: Vec<i32> = set.into_iter().collect();
        assert_eq!(v, vec![-2, 1, 5, 11, 14, 22]);
    }

    #[test]
    fn test_sub() {
        let a: TreeSet<i32> = vec![-5, 11, 22, 33, 40, 42].into_iter().collect();
        let b: TreeSet<i32> = vec![-12, -5, 14, 23, 34, 38, 39, 50].into_iter().collect();

        let set: TreeSet<i32> = &a - &b;
        let v: Vec<i32> = set.into_iter().collect();
        assert_eq!(v, vec![11, 22, 33, 40, 42]);
    }

    #[test]
    fn test_zip() {
        let mut x = TreeSet::new();
        x.insert(5);
        x.insert(12);
        x.insert(11);

        let mut y = TreeSet::new();
        y.insert("foo");
        y.insert("bar");

        let x = x;
        let y = y;
        let mut z = x.iter().zip(y.iter());

        assert_eq!(z.next().unwrap(), (&5, &("bar")));
        assert_eq!(z.next().unwrap(), (&11, &("foo")));
        assert!(z.next().is_none());
    }

    #[test]
    fn test_from_iter() {
        let xs = [1, 2, 3, 4, 5, 6, 7, 8, 9];

        let set: TreeSet<i32> = xs.iter().map(|&x| x).collect();

        for x in xs.iter() {
            assert!(set.contains(x));
        }
    }

    #[test]
    fn test_debug() {
        let mut set = TreeSet::new();
        let empty: TreeSet<i32> = TreeSet::new();

        set.insert(1);
        set.insert(2);

        assert_eq!(format!("{:?}", set), "{1, 2}");
        assert_eq!(format!("{:?}", empty), "{}");
    }

    #[test]
    fn test_comparator_iterator() {
        use compare::{Compare, natural};

        let mut m = TreeSet::with_comparator(natural().rev());

        assert!(m.insert(3));
        assert!(m.insert(0));
        assert!(m.insert(4));
        assert!(m.insert(2));
        assert!(m.insert(1));

        let mut n = 5;
        for &t in m.iter() {
            n -= 1;
            assert_eq!(t, n);
        }
        assert_eq!(n, 0);
    }

    #[test]
    fn test_comparator_borrowed() {
        use compare::{Compare, natural};

        let mut m = TreeSet::with_comparator(natural().borrowing());

        assert!(m.insert("a".to_string()));

        assert!(m.contains("a"));
        assert!(m.contains(&"a"));
        assert!(m.contains(&"a".to_string()));

        assert!(m.remove("a"));
        assert!(!m.remove(&"a"));
        assert!(!m.remove(&"a".to_string()));
    }
}